1. Technical Field
The present invention relates in general to an improved multimedia computer system and in particular to an efficient method for bus allocation in a multimedia computer system. Still more particularly, the present invention relates to a bus allocation technique which guarantees bus access for a selected input/output device at a predetermined data rate.
2. Description of the Related Art
The interchange of data within a data processing system is a well known feature of modern state-of-the-art computer systems. Text and graphics data may be efficiently interchanged between the various subsystems within a computer system utilizing well known bus techniques; howewer, modern computer systems have begun to utilize so-called "multimedia" data. That is, presentations containing audio, video, text, graphics and image combined into a common presentation.
One common characteristic of multimedia data is that the data must be presented in a time domain sensitive manner which is acceptable to human sensory systems. For example, video data, in the form of full motion pictures, typically requires precisely timed updates at a rate of twenty-four to thirty frames of data per second within the video subsystem refresh memory. This information is typically stored within the computer system as compressed data and retrieved from a mass storage device or network connection. Similarly, audio data, even if stored in a compressed manner, must be presented at timed rates which are necessary to faithfully produce human speech, music or other audio in a manner which is acceptable to the human ear.
Thus, multimedia and other real time input/output devices in a personal computer system must receive and transmit data at guaranteed time intervals. Typically these devices are attached to a bus which is shared by other devices which may or may not have stringent time interval requirements. It is thus undesirable to have these time critical input/output devices gain control of the bus and transfer data while excluding all other devices from utilizing the bus until all data transfer for a time period is complete. Further, normal bus arbitration mechanisms employed within such computers typically do not include mechanisms to assure that these time critical data transfers are performed when required. This is particularly true when more than one time critical input/output device is coupled to a computer bus.
Thus, it should be apparent that a need exists for a method and system for efficient bus allocation in a multimedia computer system or other time sensitive data transfer systems which can be utilized to guarantee bus access for particular input/output devices at a predetermined data rate.